I'm also at a disadvantage because I don't own an old Electra so I'll have to make some guesses.

If we are talking about a Brake switch that operates the rear brake light there should be two of them. One at the front brake lever and one connected to the foot operated lever.

If we are talking about a Neutral switch (assuming there is a electric starter) it will probably be mounted on the gearbox or gearbox cover(s). It's job would be to prevent the electric starter motor from running if the transmission was not in neutral.Seeing that there is no electrical devices in the transmission other than possibly this switch it would be the only thing that has a electrical wire connector.

Now, if we are talking about some other "break neutral" switch it might be on the handlebar clutch lever.On most bikes with electric starters there is a switch there so the electric starter will operate after the clutch lever is pulled in, even though the transmission is in gear.